Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $48.76   6.868%   $52.1088   $52.11   $52.10   $52.10  
  Purchase #2 $188.57   4.816%   $197.6515   $197.65   $197.65   $197.70  
  Purchase #3 $58.35   10.391%   $64.4131   $64.41   $64.40   $64.40  
  Purchase #4 $26.65   10.106%   $29.3432   $29.34   $29.35   $29.30  
  Purchase #5 $168.32   8.508%   $182.6407   $182.64   $182.65   $182.60  
  Purchase #6 $177.44   7.123%   $190.0791   $190.08   $190.10   $190.10  
  Purchase #7 $164.30   7.375%   $176.4171   $176.42   $176.40   $176.40  
  7 purchase totals = $832.39       $892.6535   $892.65   $892.65   $892.60